This application is the U.S. national phase of International Application No. PCT/EP2009/000222, filed 15 Jan. 2009, which designated the U.S. and claims priority to DE Application No. 10 2008 006 261.8 filed 25 Jan. 2008, the entire contents of each of which are hereby incorporated by reference.
The invention relates to a multilayer, flexible planar material for delimiting a matrix supply space during the production of fibre-reinforced plastic components from fibre composite semifinished products by means of an injection process for injecting matrix material, the planar material having a gas-permeable, but matrix-impermeable diaphragm, a gas-impermeable sheet and also a highly gas-permeable spacer layer which is arranged between the diaphragm and the sheet and holds the sheet at a distance from the diaphragm when a reduced pressure is generated between the diaphragm and sheet.
In the production of fibre-reinforced plastic components, use is made, as is known, of initially dry fibre composite semifinished products (“preforms”) which are saturated with free-flowing, curable matrix material in the form of resin. The dry fibre composite semifinished product may in this case be in the form of a woven fabric, a multiaxial ply or a warp-reinforced unidirectional semifinished product and consists in particular of carbon fibres, glass fibres, aramid fibres, boron fibres or hybrid materials.
A process for producing fibre-reinforced plastic components is known as a resin film infusion (RFI) process. In this process, a dry carbon fibre woven fabric or ply is deposited in a curing device and covered from the outside with a defined amount of resin film. Subsequently, the plastic component, which consists of the carbon fibres and the resin, is cured in an autoclave or another pressurised vessel under pressure and temperature. However, the use of pressurised vessels and the complex tools necessary for this purpose are very costly. Furthermore, a process of this type is difficult to handle with regard to temperatures and pressures. In addition, the available autoclaves limit the size of the plastic components to be produced.
In order to avoid these drawbacks, a process which is described in DE 100 13 409 C1 and is referred to as a “VAP” (vacuum assisted process) has already been developed. In this process a multilayer, flexible planar material is used to delimit a matrix supply space in which the semifinished product is arranged. In the prior development, the planar material consists of a plurality of layers which are separate from one another and can be handled independently of one another, namely the gas-permeable, but matrix-impermeable diaphragm, a highly gas-permeable spacer layer and also a gas-impermeable sheet. These layers are individually placed, one after another, over a flow aid layer which is placed onto the semifinished product. If the region between the sheet and the diaphragm is now evacuated and a reduced pressure is as a result built up, the pressure is accordingly reduced through the diaphragm even in the interior matrix supply space, as a result of which liquid resin is drawn out of an external resin container into the matrix supply space. Although the diaphragm in this case allows gases to escape from the matrix supply space into the spacer layer and from there toward the exterior, it at the same time retains the resin in the matrix supply space, so the resin can infiltrate the semifinished product.
Although this VAP has considerable advantages over the processes using autoclaves, the fact that each individual layer of the planar material, namely the diaphragm, the spacer layer and also the gas-impermeable sheet, has to be successively placed over the semifinished product very exactly and in a stress-free manner is somewhat problematic. This is correspondingly time-consuming and can, if it is not carried out with corresponding precision, adversely influence process safety and lead to non-uniform accumulations of matrix material.